Optimization of Transglutaminase Cross-linking of Pumpkin Oil Cake Globulin; Improvement of the Solubility and Gelation Properties

Abstract

Enzymatic cross-linking of hull-less pumpkin oil cake globulin was studied using microbial transglutaminase. Response surface methodology was employed to study the effect of enzyme/substrate ratio, temperature, and reaction time on protein cross-linking reaction, measured by degree of polymerization (DP) as a response. The second-order polynomial model showed good fit with the experimental data since the coefficient of determination was R2 = 0.9297. Reaction time of 39.2 min, E/S ratio of 1/4.9 (w/w) and temperature of 28 °C were found to be optimal conditions to achieve the highest value of DP (69%). The solubility and gelation properties of the cross-linked proteins with different values of DP were assessed for improvement. The solubility of polymerized proteins was increased over the pH range 5.0-8.0 and affected with increase of DP, at each pH value studied. The highest solubility was achieved at DP of 60%, at pH 7.0 and was 24-fold higher than solubility of unmodified protein. Gelation properties of cross-linked protein were also improved and the highest decrease of least gelation concentration was achieved at pH 9.0. © 2011 Springer Science+Business Media, LLC.